Considerable evidence has accumulated implicating the hypothalamus in the control of feeding and drinking behavior. Very little information is available relating these hypothalamic motivational mechanisms to either the sensory information relevant to eating, or to the motor control of the behavior --chewing, licking, and swallowing. This research will investigate how these three systems -- buccal afferents, reflexes of ingestion and deglutition, and hypothalamic motivational mechanisms -- interact to produce normal feeding behavior. Food seeking behavior in most mammals involves a complicated sequence of learned and unlearned behaviors. To simplify analysis at the neural level, this research will use gustatory stimuli, and the ingestion and rejection responses elicited by gustatory stimuli as a model of feeding behavior. Taste solutions have relatively simple stimulus dimensions, yet provide reliable behavioral responses which are subject to change by motivational variation. The most complex and variable behaviors associated with feeding and drinking are eliminated; the sensory-motor systems involved are minimized, but the basic characteristics of the feeding and drinking process are retained. Acute and chronic electrophysiological recording will be used to determine the effects of gustatory stimuli on thalamic and hypothalamic neural activity under varying motivational conditions. Hypothalamic feeding and drinking sites will be stimulated to test the effects these areas have on the receptive fields which elicit ingestion reflexes. Experimental degeneration methods will be applied to determine the neural pathways which subserve each of these effects. Finally, in order to determine the behavioral capacity of brainstem reflex mechanisms, the nature and intensity of oral stimuli necessary to elicit ingestion and rejection responses will be compared in normal and chronic decerebrate rats. BIBLIOGRAPHIC REFERENCES: Norgren, R. Taste pathways to hypothalamus and amygdala. J. Comp. Neurol., 166: 17-30 (1976). Norgren, R., and H. J. Grill, Efferent distribution from the cortical gustatory area in rats. Neuroscience Abstracts, Sixth Annual Meeting, Vol. II. pg. 124 (1976).